Panic is a sudden sensation of fear which is so strong as to dominate or prevent reason and logical thinking, replacing it with overwhelming feelings of anxiety and frantic agitation consistent with an animalistic fight-or-flight reaction. Panic may occur singularly in individuals or manifest suddenly in large groups as mass panic (closely related to herd behavior).

The word panic derives from the Greekπανικός, "pertaining to shepherd god Pan", who took amusement from frightening herds of goats and sheep into sudden bursts of uncontrollable fear. The ancient Greeks credited the battle of Marathon's victory to Pan, using his name for the frenzied, frantic fear exhibited by the fleeing enemy soldiers.

Prehistoric men used mass panic as a technique when hunting animals, especially ruminants. Herds reacting to unusually strong sounds or unfamiliar visual effects were directed towards cliffs, where they eventually jumped to their deaths when cornered. Humans are also vulnerable to panic and it is often considered infectious, in the sense one person's panic may easily spread to other people nearby and soon the entire group acts irrationally, but people also have the ability to prevent and/or control their own and others' panic by disciplined thinking or training (such as disaster drills). Architects and city planners try to accommodate the symptoms of panic, such as herd behavior, during design and planning, often using simulations to determine the best way to lead people to a safe exit and prevent congestion (stampedes). The most effective methods are often non-intuitive. A tall column, approximately 1 ft (300 mm) in diameter, placed in front of the door exit at a precisely calculated distance, may speed up the evacuation of a large room by up to 30%, as the obstacle divides the congestion well ahead of the choke point.[citation needed]

An influential theoretical treatment of panic is found in Neil J. Smelser's Theory of Collective Behavior. The science of panic management has found important practical applications in the armed forces and emergency services of the world.

Many highly publicized cases of deadly panic occurred during massive public events. The layout of Mecca was extensively redesigned by Saudi authorities in an attempt to eliminate frequent stampedes, which kill an average of 250 pilgrims every year.[1]Football stadiums have seen deadly crowd rushes and stampedes, such as at Hillsborough stadium in Sheffield, England, in 1989 when 96 people were killed in a deadly crush.